#86 Add empty but not emptyIterable test case

common_test.go

@@ -29,9 +29,21 @@ func testBeforeAndAfter[T any](t *testing.T, itb gcf.Iterable[T]) {
 // On function called with emptyIterable should be emptyIterable.
 func testEmptyChain(t *testing.T, f func(itb gcf.Iterable[int]) gcf.Iterable[int]) {
 	t.Helper()
-	itbe := gcf.FromSlice([]int{})
-	t.Run("is empty Iterable", func(t *testing.T) {
-		itb := f(itbe)
+	t.Run("is emptyIterable", func(t *testing.T) {
+		itb := gcf.FromSlice([]int{})
+		itb = f(itb)
 		assert.True(t, gcf.IsEmptyIterable(itb), "%v", gcf.ToSlice(itb))
 	})
+	t.Run("is empty but not emptyIterable", func(t *testing.T) {
+		defer func() {
+			err := recover()
+			if err != nil {
+				t.Errorf("%v", err)
+			}
+		}()
+		itb := gcf.FromSlice([]int{1})
+		itb = gcf.Filter(itb, func(v int) bool { return false })
+		itb = f(itb)
+		_ = gcf.ToSlice(itb)
+	})
 }